Light weight, tear resistant fabric is desired for many purposes including, but not exclusively, tents, tarps, awnings, canopies, marine coverings and banners. Attempts to provide fabrics suitable for these uses have included laminating or coating the fabric with resinous material such as rubber. Another solution to the problem of improving fabric tear resistance includes weaving the fabric itself from yarns known for their strength such as yarns made from poly(p-phenylene terephthalamide), PPD-T and poly(m-phenylene isophthalamide), MPD-I.
Laminated fabrics, even those reinforced by using some percentage of yarns either made from staple fibers or filaments of PPD-T or MPD-I such as described in Japanese Publication Kokoku Sho 62-26900, have not met the need of providing a tear resistant, light weight and economical fabric. In particular laminated fabrics do not breath, that is they do not allow moisture vapor to pass though the fabric. This is especially a problem in fabrics used as tent material or for coverings that must allow passage of vapor.
Consider tents, for example, made of coated or laminated fabrics. In cold climates or on cold nights, water vapor, which is the natural product of cooking and normal life activities, remains within the space enclosed under a laminated fabric tent. Heating causes the water vapor to rise to the top of the enclosed area where the water vapor is cooled by contacting the cold laminated surface. Moisture then condenses on this cooler surface as droplets that can rain or weep down on the tent occupants. Additionally when laminated or coated fabric is sewn into tents or products for other uses, the laminated or coated fabric does not self seal around the holes made in the fabric by the sewing needle. Holes remain open along seams, hems and other stitched areas. If this sewn laminated fabric cover is used outside, moisture from rain or other wet weather conditions can flow through the needle holes allowing moisture to reach whatever the cover was designed to protect. Finally laminated or coated fabric is generally not light weight or flexible making it difficult to move, fold, store and handle.
A non laminated fabric may be acceptable for a variety of purposes, particularly if the fabric is strong and tear resistant. Fabrics made entirely of very strong polymer fibers such as those made from PPD-T, or MPD-I, may provide sufficient strength, but may be more costly than is practical for the planned end use.